Final answer:
The difference in time between different longitudes is determined based on the 15-degree intervals and the fact that every 15 degrees equals 1 hour. The time difference can be calculated by dividing the longitude difference by 15 and rounding up if necessary.
Step-by-step explanation:
To find the difference in time between two longitudes, we need to calculate the time difference based on the 15-degree intervals.
a) The difference between 10° E and 40° E is 3 hours. Since every 15 degrees signifies a time difference of 1 hour, the 30 degree difference between 10° and 40° corresponds to 2 hours, and rounding it up makes it 3 hours.
b) The difference between 40° W and 40° E is 6 hours. Since 180 degrees corresponds to 12 hours, the 80 degree difference between 40° W and 40° E would be half of that, making it 6 hours.
c) The difference between 15° W and 60° E is 9 hours. Using the same logic as before, the 75 degree difference corresponds to 5 hours, and adding 4 hours to that gives us a total of 9 hours.